1. Field of the Invention
The present invention relates to a sheet processing apparatus that aligns sheet-like recording media such as sheets of paper, recording paper, transfer paper, or transparencies (simply referred to as “sheets” in the present specification) conveyed thereto and binds the sheets into a bundle, an image forming system including the sheet processing apparatus and an image forming apparatus such as a copying machine, a printer, facsimile, or a digital multifunction peripheral, and a sheet processing method implemented in the sheet processing apparatus.
2. Description of the Related Art
Conventionally, there is known a stapler-equipped device called a finisher that stacks sheets having been discharged from an image forming apparatus on a staple tray, and aligns the sheets in a conveying direction (so-called a “longitudinal direction”) and a direction perpendicular to the conveying direction (so-called a “width direction”), and then staples the sheets together. When stapling the edge of sheets with the stapler, the device can change a stapling position by moving the stapler in the direction perpendicular to the sheet conveying direction along an end (usually, a trailing end) of the sheets in contact with a reference fence which defines the position of the sheets in the conveying direction. At this time, in order to improve the accuracy in the alignment of a bundle of the stapled sheets, it is sufficient to maintain the posture of the trailing end of the sheets stacked on the staple tray. Therefore, there is known a configuration to press a bundle of sheets down while the trailing end of the bundle of the sheets is in contact with the reference fence. This configuration is implemented by a trailing end press lever illustrated in FIG. 1 to be described later; the trailing end press lever is provided at the bottom portion of a trailing end reference fence 51 so as to press the trailing end of a sheet bundle SB accommodated in the trailing end reference fence 51, and is configured to be capable of reciprocating in directions nearly perpendicular to an edge binding tray F.
However, in a configuration of a conventional edge binding unit (a configuration for maintaining the posture of the trailing end of sheets on a staple tray), sheets are aligned with the trailing end of the sheets abutting on a reference fence, and a positional relation in the conveying direction between the reference fence and a stapling unit is fixed during edge binding processing. Therefore, there has been a problem that the binding position in a sheet conveying direction in edge binding processing cannot be adjusted to a position that each user intends to set.
To cope with this problem, for example, Japanese Patent Application Laid-open No. 2008-156073 discloses the invention of a sheet processing apparatus that performs a predetermined process on a conveyed sheet member and discharges the processed sheet member; in this invention, in order to eliminate the need for a retracting mechanism of a binding device and a drive source of a trailing end fence thereby decreasing the size of the apparatus and reducing a production cost, the sheet processing apparatus includes an intermediate tray on which a conveyed sheet member is temporarily stacked; a trailing end fence that is in contact with the trailing end of a plurality of sheet members stacked on the intermediate tray and conveys the sheet members to a delivery position; an ejection claw that takes over the conveyance of the sheet members from the trailing end fence at the delivery position and conveys the sheet members from the intermediate tray; and a conveyance drive mechanism that drives the trailing end fence and the ejection claw by driving force of a single motor.
Furthermore, Japanese Patent Application Laid-open No. 2009-263127 discloses the invention of a sheet post-processing apparatus; in this invention, in order to align sheets by bringing a leading end stopper into contact with the leading end of the sheets certainly, the sheet post-processing apparatus includes a discharge roller that conveys a sheet discharged from an image forming apparatus, and stacks the sheet on an alignment tray provided at a slant; and a movable leading end stopper that presses the leading end of sheets stacked on the alignment tray and brings the trailing end of the sheets into contact with an abutting surface of a reference fence, thereby aligning the sheets in a conveying direction. The invention discloses the sheet post-processing apparatus in which a pressing amount of the leading end stopper to press sheets is variable.
However, in the invention disclosed in Japanese Patent Application Laid-open No. 2008-156073, the trailing end fence enables the delivery of a sheet member to the ejection claw, but is unable to adjust the binding depth. Furthermore, in the invention disclosed in Japanese Patent Application Laid-open No. 2009-263127, the reference fence on which the trailing end of sheets abuts when in the sheets are aligned in the sheet conveying direction is fixed, and accordingly, the binding position (binding depth) in the sheet-conveying direction in edge binding processing cannot be adjusted to a position that each user intends to set.
The present invention has been made in view of the above background, and there is a need for providing a compact and inexpensive sheet processing apparatus capable of allowing each user to arbitrarily set the binding position from an end face of a sheet bundle.